Liquid glue composition



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Patented Nov. 3, 1953 UNITED S ATE-S 2 NT OFFICE 2,658,001 LIQUID GLUE COMPOSITION Illinois No Drawing; Application September 26, 1950,

Serial N0. 186,919

14 Claims. (01. 106-1s5)' This inve'ntion-relates generally to adhesivecompositions, and more particularly to an im-' provedliquid animal glue and to the method'of its production;

It h'asbeen known for some time that the presence of various substances in glue'solutions' prevents the formation of tough gels when the glue solutions are cooled, and it has been the general practice'to prepare'liquid glues by'adding a liquefying agent, such as thiourea', to the glue solutions. Certain of the common liquefying agents; such as thiourea, are rather expensive, however, and whereas theymay be otherwise'i satisfactory'as 'liquefyin'g agents, their cost hasmade their use either pr'ohibitivebr has substantially increased the cost of the liquid glue. More-" over, liquid glues made with thiourea'as thelique-' fying' agent, in addition to be relatively eapensive, exhibit a markedtendency to thin out rapid ly and forma flocculent precipitate on aging. As the foregoing characteristics detract appreciably from the valueof the liquid glue'product, there has been a'strong demand for an improved'liquefying agent.

It has also been known for many years that thiocyanate salts are more powerful liquefying I agents than thiourea and are much less 'expensive. While there has been strong economic pressure onthe'glueindustry to employ thiocyanate'salts as liquefying agents,'it has not'been possible to take advantage of this opportunity to* lower the production cost and improve theproduct' in the foregoing manner because the watersoluble 'thiocyanate salts produce a blood-red coloration in the presence 'of water-soluble iron salts. Since the glue potsandthe apparatus with which the liquid glue is applied almostinvariably contain iron, as de the containers in which the glue isnormallyshipped andstored, ithas been impossible for'practical-reasons to entirely eliminate contaminating the liquid glue solutions with iron. Until the present invention, therefore, it has" been commercially impossible toemploy' the more efiicie'nt'and l'essexpensive thiocyanate salts as liquefying agents for the preparation'of commerical' liquid glues."

An object of the present invention is to provide an improvedliquid animal glue containing-a thiocyana'te salt-asa liquefying agent-which will not discolor in the presence of soluble'iron salts.

Aiurtherobject of the invention is 'to provide" a 'less eX-pensiveliquid animal-glue which-Will not discolor in the presence of solubleironsalts;

still anotherobjectof the invention is to provide a simpleand'effibient process for the prep-*- aration of an animal liquid glue'containing a thio-' cyanate salt as a 'liquefying agent which will not discolor in the presence of soluble iron salts.

Other objects of the invention will be apparent from the descriptionand claims.

It has been discovered that an improved liquid animal glue having powerful adhesive properties can be made by admixing with an animal glue solution containing a thiocyanate salt as a liquefying agent a small amount o'fa water-soluble" complex hydrate of phosphorous pentoxide, such as the soluble pyropho'sphates, the hexameta phosphates, or the polyphosphate's. When a small amount of a water-soluble salt of a com plex phosphate is incorporated in an animal glue composition having a water-soluble thio'cyanate salt as a liquefying agent, the objectionable blood-red discoloration normally developed when a glue composition liquefied with a thiocyanate is contaminated with iron will be permanently prevented. V V

In accordance with the present invention, liquid animal glues which have been prepared with a thiocyanate salt as the liquefying agent may be,

rendered capable of resisting discoloration due to contamination with iron by incorporating in said liquid glue a small percentage of a watersoluble complex phosphate compound. Of particular utilityare the alkali metal pyrophosphate salts, the alkali metal hexamctaphosphate salts,

and the alkali metal polyorthophosphate salts,

or the corresponding known ammonium and acid salts of the foregoing groups of complex phosg phate salts. The various water-soluble complex:

phosphate salts may also be mixed in varying proportions for use in the present invention, I

While it has been found that trisodium orthophosphate and the other orthophosphate salts are unsuitable for use in the herein-disclosed animal glue composition, the water-soluble poly:

orthophosphate salts of polyphosphates can be used very satisfactorily since they eiiectively prevent discoloration due to iron contamination and-can be used in amounts which do not raise the pH of the glue solution above a maximum value of 8f The simple orthophosphate salts form iron-compositions which are not entirely insoluble in the animal glue solution. Thus,

when trisodium orthophosphate, for example, is

employed in an animal glue solution containing.

ammonium thiocyanate as a liquefying agent, it is necessary, in order to prevent iron'discoloratiom' to add the orthophosphate in amounts which raise the pH of the animal glue solution sub-",

stantially above the pH of 8. This causes both the animal protein of the glue and the ammonium thiocyanate to break down so that the adhesive properties of the animal glue solution are destroyed. The polyorthophosphate salts, however, and the other complex phosphates such as tetrasodium pyrophosphate form iron phosphate compositions which are substantially insoluble in the animal glue composition and consequently do not have to be used. in amounts which raise the pH of the glue above a maximum of 8. The hexametaphosphate salts which are substantially neutral and the monoand disodium pyrophosphate salts which are acidic also form insoluble iron phosphate compositions so that iron discoloration of an animal glue solution containing a thiocyanate liquefying agent is effectively prevented. These latter salts, of course, do not present the problem of making the animal glue solution excessively alkaline.

In a liquid animal glue solution containing a thiocyanate as a liquefying agent which has incorporated therewith approximately 0.5 per cent sodium pyrophosphate based on the weight of the liquid glue, the permanent formation of the characteristic blood-red color normally occurring when the glue is contaminated with iron is prevented under the following conditions:

TABLE 5% dilution with FeCh solution containing 2800 ppm Fe.

33% dilution with FeCla solution containing 700 ppm. Fe.

67% dilution with FeCla solution containing 450 ppm. Fe.

100% dilution with FeCla solution. containing 360 ppm. Fe.

It is apparent from the data set forth in the table that when 0.5 per cent sodium pyrophosphate is added to a liquid animal glue containing a solubilizing thiocyanate salt, there is no discoloration when 5 per cent of a ferric chloride solution containing 2800 parts per million ferric iron is added to the liquid glue. Likewise, there is no discoloration of the said liquid glue solution when there is 100 per cent dilution with a ferric chloride solution containing 360 parts per million ferric iron.

It has been found that when the foregoing liquid glue solution containing a thiocyanate salt as a solubilizing agent is treated in the foregoing manner with a 1, 3, or 5 per cent solution of sodium pyrophosphate, there is no material improvement in the resistance of the liquid glue to discoloration when diluted with the ferric chloride solutions set forth in the table over that obtained when only 0.5 per cent solution of the sodium pyrophosphate is used. Likewise, 1.0 per cent of solution of sodium hexametaphosphate produces results very similar to those obtained when a 1.0 per cent sodium pyrophosphate solution is added to the liquid glue containing a soluble thiocyanate compound.

The efiiciency of the color-repressing, watersoluble derivatives of the phosphorus oxyacid compounds is not adversely influenced by variations in the pH of the solution. Highly satisfactory results are obtained when the liquid animal glue solutions are diluted with the ferric chloride solutions having the concentrations set forth in the table wherein the pH values ranged from approximately 6.1 to 7.0 for the solutions containing sodium pyrophosphate and from 5.8 to 5.6 for the solutions containing sodium hexametaphosphate.

As animal glue compositions are adversely affected by strongly alkaline or strongly acidic compositions and cannot be maintained in a stable form at excessively high or low pH values, it is desirable to maintain the pH value of the herein-disclosed animal glue compositions be tween a pH of about 5 and 8 and preferably between a pH of 6.5 to '7.

In accordance with the present invention, when between approximately 0.5 per cent and 5.0 per cent of a water-soluble complex phosphate salt compound is incorporated in a liquid animal glue solution containing a soluble thiocyanate salt as a liquefying agent, all discoloration due to iron contamination is permanently prevented. Since the use of 1, 8, 5, or larger percentages of the soluble complex phosphate compounds do not materially improve the resistance of the liquid glues to discoloration due to iron contamination over that obtained when 0.5 per cent of a watersoluble complex phosphate compound is used, it is preferred to employ phosphate concentrations between 0.5 per cent and 1.0 per cent based on the weight of the liquid glue solution.

As a specific illustration of the present invention, the following example is given:

Example 1 part of sodium pyrophosphate is dissolved in 48 parts of water. To this solution is then added 5.8 parts of ammonium thiocyanate and the compositions thoroughly mixed. To the foregoing mixture is added 46.2 parts of animal glue and the mixture allowed to soak for approximateyl 1 hr. or until softened. The mixture is then heated until the glue melts and is stirred until a uniform product is obtained.

In the foregoing example, the amount of phosphate employed is slightly less than 1 per cent of the weight of the liquid glue. It should be under stood, however, that the proportions of the ingredients may be varied considerably. Likewise, the procedure of preparing the adhesive composition may be varied to suit the particular conditions existing. For example, the animal glue may be first mixed with water and allowed to stand without heating. The mixture may then be heated to approximately C. to complete the dispersion of the glue. The liquefying agent and the said phosphate compound may then be added and thoroughly dispersed throughout the glue until a uniform product is obtained. The resulting liquid and glue may then be strained. if necessary, and cooled. It is evident that the phosphate compound may be added in the form of a solution or as a solid, whichever process of preparing the liquid glue is followed. If desired, the improving ingredients may be added in the same proportions directly to the evaporated glue liquor containing the necessary amount of glue solids rather than by reconstituting the dried glue.

Liquid animal glue solutions made in accordance with the foregoing invention produce bonds equally as strong and generally stronger than those produced by other liquid glues. Shear tests made on maple blocks glued with a liquid glue made in accordance with the present invention gave values above 2000 pounds per square inch.

Since applicants invention resides in the combination of a soluble complex phosphate compound with a liquefying thiocyanate salt, it is not necessary to describe in detail the various suitable commercial water-soluble thiocyanates which may be employed as liquefying agents. It

ammonia may be said, however, that among those suitable are ammonium, sodium, and potassium thiocyanates, although many others might also be used.

Various plasticizing agents, wetting agents, solvents, anti-foaming agents, and filling materials may be used in conjunction with the preferred adhesive for the purpose of obtaining special eiiects for which the use of such materials is known to the adhesive art without departing from the scope of the present invention.

It should be understood also that the adhesive formula given above is for the purpose of illustrating the novel character of the invention and for the purpose of making clear the principle by which the new and improved result is obtained. It is not desired to limit the invention by the specific example, since numerous variations may be made in the adhesive base and in the proportions of the other ingredients used without departing from the limits defined as essential to the invention.

In the specification and claims the term complex as applied to applicants phosphate compositions is employed to designate those phosphates which are derived by combining two or more molecules of the foundation acid; and includes the pyrophosphates M4P2O7, the hexametaphosphates (HPO3)6, and the polyphosphates derived from two or more molecules of orthophosphoric acid by the elimination of one or more molecules of water and which have two or more phosphorus atoms per molecule.

In the claims which follow, the term alkali is intended to include the ammonium salts as well as the alkali metal salts.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

This application is a continuation-in-part application of United States application Serial No..

2,326, filed January 14, 1948, now abandoned.

We claim:

1. A color stabilized liquid animal glue composition comprising an aqueous solution of an animal glue having a thiocyanate compound as a liquefying agent therefor with a water-soluble complex hydrate of phosphorous pentoxide in sufficient amount to be effective as a repressant against discoloration normally occurring when a liquid animal glue composition containing a thiocyanate compound is contaminated with iron, said stabilized glue composition having a maximum pH of about 8.

2. A color stabilized liquid animal glue composition substantially as described in claim 1 wherein the complex hydrate of phosphorous pentoxide is present in an amount between about 0.5 and 5.0 per cent.

3. A color stabilized liquid animal glue composition comprising an aqueous solution of an animal glue containing a thiocyanate compound as a liquefying agent and a complex phosphate ion-producing compound in sufficient amount to be efiective as a repressant against discoloration normally occurring when a liquid animal glue composition containing a thiocyanate compound is contaminated with iron, said stabilized glue composition having a maximum pH of about 8.

4. A color stabilized liquid animal glue composition substantially as described in claim 3 wherein the complex phosphate ion-producing compoundis' present in an amount betweenrabout 0.5. and 5.0 per cent. 1

.5. A color stabilized liquid animal glue composition comprising an aqueous solution of an animal glue containing a water-soluble thiocyanate compound as a liquefying agent and between about 0.5 and 5.0 per cent of an alkali pyrophosphate as a repressant against discoloration normally occurring when a liquid glue composition containing a soluble thiocyanate compound is contaminated with iron, said stabilized glue composition having a maximum pH of about 8.

6. A color stabilized liquid animal glue com position comprising an aqueous solution of an animal glue containing a water-soluble thiocyanate compound as a liquefying agent and between about 0.5 and 5.0 per cent of an alkali hexametaphosphate as a repressant against discoloration normally occurring when a liquid glue composition containing a soluble thiocyanate compound is contaminated with iron, said stabilized glue composition having a maximum pH of about 8.

7. A color stabilized liquid animal glue composition comprising an aqueous solution of an animal glue containing a water soluble thiocyanate compound as a liquefying agent and between about 0.5 and 5.0 per cent of an alkali polyphosphate as a repressant against discoloration normally occurring when a liquid glue composition containing a soluble thiocyanate compound is contaminated with iron, said stabilized glue composition having a maximum pH of about 8.

8. A method of preventing the discoloration of a liquid animal glue containing a thiocyanate compound as a liquefying agent, comprising dispersing throughout the said liquid animal glue containing a thiocyanate compound in sufiicient amount to be effective as a repressant against discoloration a water-soluble complex hydrate of phosphorous pentoxide without raising the pH of the said glue above about 8.

9. A method substantially as described in claim 8 wherein the complex hydrate of phosphorous pentoxide is used in an amount between about 0.5 and 5.0 per cent.

10. A method of preventing the discoloration of a liquid animal glue containing a thiocyanate compound as a liquefying agent, comprising dispersing throughout the said liquid animal glue composition containing a thiocyanate compound a complex phosphate ion-producing compound in suilicient amount to be efiective as a repressant against discoloration without raising the pH of the said glue above about 8.

11. A method substantially as described in claim 10 wherein the complex phosphate ionproducing compound is used in an amount between about 0.5 and 5.0 per cent.

12. A method of preventing a discoloration of a liquid animal glue containing a water-soluole thiocyanate compound as a liquefying agent which normall occurs when the said liquid glue is contaminated with iron, comprising dispersing throughout the said liquid animal glue containing the soluble thiocyanate compound between about 0.5 and 5.0 per cent of an alkali pyrophosphate without raising the pH of the said glue above a pH of about 8.

13. A method of preventing a discoloration of a liquid animal glue containing a water-soluble thiocyanate compound as a liquefying agent which normally occurs when the said liquid glue 7 is contaminated with iron, comprising dispersing throughout the said liquid animal glue containing the soluble thiocyanate compound between about 0.5 and 5.0 per cent of an alkali hexametaphosphate without raising the pH of 5 the said glue above a pH of about 8.

14. A method of preventing a discoloration of a liquid animal glue containing a water-soluble thiocyanate compound as a liquefying agent which normally occurs when the said liquid glue is contaminated with iron, comprising dispersing throughout the said liquid animal glue containing the soluble thiocyanate compound between about 0.5 and 5.0 per cent of an alkali polyphosphate without raising the pH of the said glue above a pH of about 8.

HARLAND H. YOUNG. FRANK L. DE BEUKELAER.

References Cited in the file of this patent UNITED STATES PATENTS Number 10 Number Name Date Shisler Nov. 8, 1932 Pierson July 3, 1934 Schwartz Dec. 15, 1936 Schwartz Dec. 5, 1939 FOREIGN PATENTS Country Date Great Britain June 20, 1938 

1. A COLOR STABLIZED LIQUID ANIMAL GLUE COMPOSITION COMPRISING AN AQUEOUS SOLUTION OF AN ANIMAL GLUE HAVING A THIOCYANATE COMPOUND AS A LIQUEFYING AGENT THEREFOR WITH A WATER-SOLUBLE COMPLEX HYDRATE OF PHOSPHOROUS PENTOXIDE IN SUFFICIENT AMOUNT TO BE EFFECTIVE AS A REPRESSANT AGAINST DISCOLORATION NORMALLY OCCURRING WHEN A LIQUID ANIMAL GLUE COMPOSITION CONTAINING A THIOCYANATE COMPOUND IS CONTAMINATED WITH IRON, SAID STABILIZED GLUE COMPOSITION HAVING A MAXIMUM PH OF ABOUT
 8. 